The present invention relates to a novel sensor arrangement useful in sensing the position of appliance doors and particularly in sensing when refrigerator/freezer doors are open or slightly ajar.
In the case of refrigerators and freezers, it is desired to provide a warning indication to the owner when a door is open or slightly ajar so that the door can be closed and thus eliminate excessive energy usage and protect the stored food from spoiling. Sensors for this purpose have been used in the past. Typically, a well known sensor arrangement involves the use of a plunger protruding from the front frame of the refrigerator cabinet such that when the door is properly closed, it pushes back to open the contacts of a microswitch. When the door is open, the plunger moves forward until the microswitch contacts close causing a "door open" alarm to sound. Similar arrangements are used to activate interior lights.
While useful as door alarms, these arrangements have certain disadvantages. If operated at low voltages and low currents, the design of the microswitch contacts, usually gold plated, makes them expensive for appliance use. Also, it is required to provide proper plunger and housing design so as to enable them to pass wash tests and remain free from contaminants.
Magnetic devices have also been used in which either a magnet (or magnetic field sensor) has been mounted in the face frame of the refrigerator and the magnetic field sensor (or magnet) is mounted on the interior face of the door. These are less sensitive to dirt problems but are not readily adapted to slight door-ajar movements or positioning of the door.
Additionally, the use of frame mounted devices require that, for a two door appliance, the sensor arrangement be duplicated, one for each door.